Discrete element numerical simulation method for simulating rock-soil cutting in deep-sea environment

Abstract

A discrete element numerical simulation method for simulating cutting of rock-soil mass under deep-sea environment in the field of dredging technology, comprising the following steps: (1) generating a ball with a radius of r a ~ r b in the simulation area as a simulated rock-soil mass particle; (2) by scaling the ball, the porosity of the rock-soil mass particle reaches the target value, and the rock-soil mass particle is given certain attributes, so that the rock-soil mass particle gradually reaches a stress balance state under the action of gravity; (3) identifying the particles at the edge of the rock-soil mass, applying pressure perpendicular to the surface of the rock-soil mass to the edge particles to simulate the confining pressure caused by water on the rock-soil mass under deep-sea environment; (4) importing the information of the cutting tool, calculating through Newton's second law and the relative position and acceleration relationship between the tool and the rock-soil mass particles, and counting the change of the resistance of the cutting tool with time. The present application directly applies confining pressure to the edge particles of the soil, solving the problem of confining pressure in deep-sea environment cutting numerical simulation.

Description

Technical Field

[0001] This invention relates to a numerical simulation method for rock and soil cutting in the field of dredging technology, and in particular to a discrete element numerical simulation method based on mass conservation and real-time positioning for simulating rock and soil cutting in a deep-sea environment, which can realize real-time dynamic display of the topography of the entire dredging area. Background Technology

[0002] With the development of dredging technology, attention has gradually turned to the deep sea. To better develop deep-sea mineral resources, new equipment is often needed to address the high confining pressure environment of the deep sea. Reproducing the high confining pressure environment of the deep sea in the laboratory is extremely costly, leading researchers to focus on numerical simulation. However, accurately reproducing the high confining pressure environment in numerical simulation is also no easy task. How to better simulate the high confining pressure environment of the deep sea has become a key aspect of the research and development of deep-sea mining equipment. However, there is currently no suitable numerical simulation method. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a discrete element numerical simulation method for simulating rock and soil cutting in deep-sea environments. This method simulates the high confining pressure environment in deep seas by applying vertical stress to the edge particles of the rock and soil mass. It does not require additional coupling with the finite element method and can simulate the dynamic process of rock and soil cutting and fracturing at different water depths. It is also convenient to use.

[0004] This invention is achieved through the following technical solution: a discrete element numerical simulation method for simulating rock and soil cutting in a deep-sea environment, characterized by the following steps: Step 1, generating a sample with radius r within the simulation region. a ~r b The process involves four steps: First, a sphere is used as the simulated soil particles. Second, the particles are scaled to achieve a porosity of the target value 'e'. The particles are then assigned properties such as elastic modulus, density, and friction coefficient, and allowed to gradually reach equilibrium under their own weight. Third, particles at the edges of the soil mass are identified, and pressure perpendicular to the surface is applied to these particles to simulate the confining pressure exerted by water on the soil mass in a deep-sea environment. Fourth, the position and velocity of the cutting tool are imported, and calculations are performed using Newton's second law and the relative position and acceleration relationships between the tool and the soil particles. The change in resistance experienced by the cutting tool during its movement over time is statistically analyzed.

[0005] In step three, the identification of edge particles is achieved by counting the number of adjacent particles of each soil particle. When the number of adjacent particles is less than a constant n, the soil particle is considered to be an edge particle.

[0006] Furthermore, in step three, the method for determining whether a certain rock or soil particle is an edge particle is as follows:

[0007] Step 1: Identify the coordinates and radius of the center of each particle.

[0008] Step 2: Calculate the distance between the center of each remaining particle j and the center of particle i. The center coordinates of particle j are (x... j y j ), radius r j The coordinate information of the center of particle i is (x i y i ), radius r i The absolute distance between the centers of particle i and particle j can be obtained as follows:

[0009] Step 3: Determine the number n of adjacent particles of particle i. i When d ij ≤1.2*(r i +r j If a particle is adjacent to particle i, then the particle is considered to be adjacent to particle i.

[0010] Step 4: Determine if particle i is an edge particle. i When the value is less than or equal to e*N, the particle is considered an edge particle. N is a parameter based on dimension and particle type; in general two-dimensional simulations, N can be considered to be 4.

[0011] Where, r j The unit is m, d ij The unit is m.

[0012] Furthermore, the method for applying pressure perpendicular to the surface of the soil and rock mass to the edge particles is as follows:

[0013] Step 1, the coordinate information of the center of edge particle i is (x i y i ), with a radius of r i Identify the coordinate information of adjacent particles of edge particle i: (x1, y1), (x2, y2), ..., (x... n y n );

[0014] Step two: Calculate the average of the x and y coordinates of each adjacent particle. The direction of the pressure is (x) ave -x i y ave -y i );

[0015] Step 3: Calculate the pressure F exerted on particle i. i F i=ρgh•πr i 2 Where ρ is the density of seawater, in kg / m³ 3 Where g is the acceleration due to gravity, take g = 9.8 N / kg; Step four, apply pressure to the edge particle i, the magnitude of the pressure is F. i The direction is (x ave -x i y ave -y i );

[0016] Where ρ is the density of seawater, in kg / m³. 3 g is the acceleration due to gravity, taken as g = 9.8 N / kg; h is the water depth at the location of the particle, in meters; F i The pressure exerted on particle i is expressed in N.

[0017] Compared with the prior art, the present invention has the following advantages: The present invention is applicable to numerical simulation of discrete element method, and can better simulate the effect of deep-sea high confining pressure environment on rock and soil. It does not need to be coupled with finite element method during the simulation process, and is easy to use; The method of the present invention can be used for two-dimensional and three-dimensional numerical simulation, and has wide applicability. Attached Figure Description

[0018] Figure 1 This is a flowchart of an embodiment of the present invention;

[0019] Figure 2 This is a process diagram of numerical simulation according to an embodiment of the present invention;

[0020] The labels in the diagram are: 1. Cutting tool; 2. Edge particles under confining pressure; 3. Center particles without confining pressure. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] Example

[0023] The present invention is as described above. Figure 1 and 2 As shown, Figure 1 This is a schematic diagram of an embodiment of the present invention. Figure 2 This is a process diagram of the numerical simulation of the present invention.

[0024] In the implementation of this invention, the soil to be cut is generated using discrete element method software, and the soil radius r is... a ~r bThe soil is assigned density. The soil is compacted using the radius expansion method (i.e., the soil radius is first multiplied by a coefficient less than 1 to reduce its size; once the unbalanced forces between soil particles are relatively small, the radius is then divided by the coefficient to expand it back to its original size). During this process, the soil particles are assigned certain properties such as elastic modulus, density, and friction coefficient. The unbalanced forces and porosity of the soil are continuously monitored. Once the unbalanced forces within the soil are less than a certain characteristic value, the soil is considered compacted and stable, and subsequent simulation studies can be conducted.

[0025] Identify the edge particles of the soil. Step 1: Identify the coordinates and radius of the center of each particle; Step 2: Calculate the distance between the center of each remaining particle j and the center of particle i. The center coordinates of particle j are (x...). j y j ), radius r j The coordinate information of the center of particle i is (x i y i ), radius r i The absolute distance between the centers of particle i and particle j can be obtained as follows: Step 3: Determine the number n of adjacent particles of particle i. i When d ij ≤1.2*(r i +r j If n ), then the particle is considered adjacent to particle i; step four, determine whether particle i is an edge particle, when n i When the value is ≤e*4, the particle is considered to be an edge particle.

[0026] After identifying the edge particles, a confining pressure is applied to them. Step one: The coordinates of the center of edge particle i are (x... i y i ), with a radius of r i Identify the coordinate information of adjacent particles of edge particle i: (x1, y1), (x2, y2), ..., (x... n y n Step two: Calculate the average of the x and y coordinates of each adjacent particle. The direction of the pressure is (x) ave -x i y ave -y i Step 3: Calculate the pressure F exerted on particle i. i F i =ρgh•πr i 2 Where ρ is the density of seawater, in kg / m³ 3 Where g is the acceleration due to gravity, take g = 9.8 N / kg; Step four, apply pressure to the edge particle i, the magnitude of the pressure is F.i The direction is (x ave -x i y ave -y i ).

[0027] Finally, the position and speed of the cutting tool are imported, and calculations are performed using Newton's second law and the relative position and acceleration relationship between the tool and soil particles. The change of resistance to the cutting tool during its movement is statistically analyzed over time.

[0028] It should be noted that when the cutting tool cuts the soil and the soil breaks down, the edge particles also change. Therefore, the steps of identifying edge particles and applying confining pressure need to be carried out continuously in the calculation.

[0029] The specific operation of the present invention has been described above. It should be understood that the present invention is not limited to the specific operation described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of the present invention.

Claims

1. A discrete element numerical simulation method for simulating rock and soil cutting in a deep-sea environment, characterized in that, Includes the following steps: Step 1: Generate a region with a radius of [missing information] within the simulation area. r a ~ r b Spheres, used as simulated soil and rock particles; Step two involves scaling the particles to achieve the target porosity. e Then, certain properties are assigned to the soil and rock particles, and the soil and rock particles are allowed to gradually reach a state of force equilibrium under their own weight. Step 3: Identify the particles at the edge of the rock and soil mass and apply pressure perpendicular to the surface of the rock and soil mass to the edge particles to simulate the confining pressure of water on the rock and soil mass in a deep-sea environment. Step 4: Import cutting tool information, calculate the relative position and acceleration relationship between the tool and soil particles using Newton's second law, and statistically analyze the change of resistance to the cutting tool over time during its movement. In step three, the method for determining whether a certain rock or soil particle is an edge particle is as follows: Step 1: Identify the coordinates and radius of the center of each particle. Step 2: Calculate the distance between the center of each remaining particle j and the center of particle i. The center coordinates of particle j are ( x j , y j ), radius is r j The coordinate information of the center of particle i is ( x i , y i ), radius is r i The absolute distance between the centers of particle i and particle j can be obtained as follows: ; Step 3: Determine the number of adjacent particles of particle i. n i When d ij ≤ 1.2*( r i + r j If ), then the particle is considered to be adjacent to particle i; Step 4: Determine if particle i is an edge particle. n i ≤ e* When N is used, the particle is considered an edge particle; N is a parameter based on dimension and particle type, and is considered to be N=4 in two-dimensional simulation; Where, r j The unit is m. d ij The unit is m.

2. The discrete element numerical simulation method for simulating rock and soil cutting in a deep-sea environment according to claim 1, characterized in that... In step two, the properties assigned to the soil particles include, but are not limited to, elastic modulus, density, and coefficient of friction; in step four, the information of the cutting tool is imported, including, but not limited to, position and speed.

3. The discrete element numerical simulation method for simulating rock and soil cutting in a deep-sea environment according to claim 1, characterized in that, In step three, the method for applying pressure perpendicular to the surface of the soil and rock mass to the edge particles is as follows: Step 1, the coordinate information of the center of edge particle i is ( x i , y i ), radius is r i Identify the coordinate information of adjacent particles of edge particle i. x 1, y 1), x 2, y 2), ..., ( x n , y n ); Step two: Calculate the average of the x and y coordinates of each adjacent particle. , Then the direction of the pressure is (xave-xi, yave-yi). Step 3: Calculate the pressure on particle i F i , ; Step four, apply pressure to edge particle i, the pressure magnitude is F i The direction is ( x ave - x i , y ave - y i ); in, ρ The density of seawater is expressed in kg / m³. 3 ; g Let be the acceleration due to gravity, and take . g =9.8N / kg; h The water depth at the location of the particle, in meters (m). F i The pressure exerted on particle i is expressed in N.

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